1. Field of the Invention
The present invention relates to a method of manufacturing an aqueous dispersion of fortified rosin for use in paper sizing, and more particularly to a method of manufacturing the same by the phase inversion process from W/O or water-in-oil type dispersion to O/W or oil-in-water type in the presence of an effective dispersing agent thus far not used in paper sizing.
2. Description of Material Information
Aqueous dispersions of rosin and its derivatives have been widely used in paper sizing and are commonly known as rosin sizes. The sizing process involves the separate addition of a dilute aqueous dispersion of rosin size and alum to a pulp slurry. Fortified rosins are made by adducting an .alpha.,.beta. unsaturated carboxylic acid to ordinary rosin, and essentially, mixtures comprised of unreacted rosin and adducted rosin, and are much more effective for sizing. Typical acids used are fumaric acid, acrylic acid, maleic acid, itaconic acid, citraconic acid, and the anhydrides of the latter three, although fumaric acid and maleic anhydride are by far the more common acids used. In general, if rosin is treated with formaldehyde, or with modified formaldehyde, the resultant addition product increases the efficiency of rosin sizes.
U.S. Pat. No. 3,565,755 discloses a solvent emulsifying method giving an emulsion. The process includes solving the fortified rosin in a water-insoluble, volatile organic solvent, such as benzene or toluene, mixing the solution with an aqueous solution of alkaline material, or a water-soluble salt of rosin and/or fortified rosin, homogenizing the unstable mixture to produce a stable emulsion, and removing the organic solvent by distillation. A disadvantage of this process is that the intermediate fortified rosin solution in the organic solvent is thermally unstable and tends to aggregate at higher temperatures.
Australian Patent Application No. 69365, filed on May 24, 1974, discloses a method of manufacturing aqueous rosin dispersion by homogenizing a molten rosinous substance at a temperature of about 150.degree. to about 195.degree. C. under a pressure of about 140 kg/cm.sup.2 to about 560 kg/cm.sup.2, in the presence of an anionic dispersing agent, including saponified rosin base material, sodium alkylbenzene sulfonate, sodium naphthalene sulfonic acid, sodium lauryl sulfate, and the ammonium salt of the sulfate ester of an alkylphenoxy (polyethyleneoxy)ethanol.
U.S. Pat. No. 4,148,665 Kulick et al. discloses that colloidal aqueous dispersions of rosin possess improved mechanical and heat stability when they contain small amount of a dissolved water-dispersible emulsifying agent selected from the group consisting of tetrasodium N-(1,2-dicarboxyethyl)-N-octadecylsulfosuccinate, disodium N-octadecylsulfosuccinate, disodium dodecylpenta(ethoxy)ethylsulfosuccinate, and disodium decylsulfosuccinate as stabilizing agent. Such dispersions are prepared by the use of organic solvent such, as toluene, and by passing the material in solution through a homogenizer and removing the solvent. In this invention the phase inversion process was not used. The formula of this invention called for 5 ethoxy groups to be present.
U.S. Pat. No. 4,203,776, to Greiner discloses a process for preparing paper size from fortified rosin by the use of the phase inversion process, using as dispersing agents salts of sulfosuccinic acid-ethylene oxide condensates having the following general formula, in which R is a normal or branched chain alkyl group containing from 4 through 18 carbon atoms, and n is an integer of 4 through 25: ##STR2## As can be seen from the formula, the presence of a benzene ring is required for these dispersing agents.
Finally, U.S. Pat. No. 4,309,338, to Okumichi et al. discloses a process for preparing an aqueous dispersion of a rosin-base material by the phase inversion process, employing at least one of the following dispersants: ##STR3## wherein R.sub.1 is a hydrocarbon residue having 4 to 18 carbon atoms, m is an integer of 1 or 2, n is an integer of 4 to 25, X is a hydrogen atom or a hydroxyl group, and M is a monovalent cation, and ##STR4## wherein R.sub.2 is a hydrogen atom or a lower alkyl group, A is a straight- or branched-chain alkylene having 2 to 3 carbon atoms, p is an integer of 4 to 25, and Q is a monovalent cation. Again, the presence of a benzene ring in the dispersants is required. The inventors pointed out that the excellent sizing effects, high mechanical and dilution stabilities, and improved foaming properties are achievable only when at least one dispersing agent fitting at least one of the above two formulae is used.